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Vegetation Layers

To learn how the VTP software represents vegetation, first read the web page VTP Implementation Vegetation.  The following assumes that you are familiar with the terminology.

VTBuilder can import vegetation data from these formats:

• ESRI Shape files (.shp)
• USGS LULC (Land Use / Land Cover, usual file extension is .gir)

There are several type of Vegetation Data.

1. Biotype - polygonal areas which describe which biotype is found in that area.
2. Density - polygonal areas which contain information (0 to 1) about how dense the vegetation is.
3. Explicit - a set of actual plant instances.

Currently you can:

• Import Biotype from Shapefiles.
• Import Density from LULC and Shapefiles.
• Read and write Explicit instances with VF files, which can also be read by VTP Enviro

Before doing any operations with vegetation,

1. Make sure that you have a species file with the species you need. An example file is is VTP/Enviro/Data/PlantData/species.xml
2. Load your species file with the menu command "Vegetation: Species List". 

If you have point data for each plant, use these steps to import explicit plant instances:

1. Use the menu command "Layer: Import Data" and indicate Vegetation.
2. Indicate the file which contains the point locations of your instances.  Generally this is a SHP file.
3. Save the resulting layer to a VF file, which can be used by Enviro.

If you have an area covered by a single plant species, use these steps to generate a vegetation distribution:

1. Use the Area Tool to indicate the area in which to distribute the vegetation
2. Give the menu command "Area Tool - Generate Vegetation"  A dialog will ask for :
   • Grid Spacing of Sampling, in meters.  The distribution will occur on a regular grid.  At each point, it will test to see what kind of plant belongs at that location, given all known inputs.  Then, if a plant is generated, a small random offset is applied to avoid the "regular" look of an evenly distribution.
   • Artificial Scarcity.  Most interactive simulation can't handle the full density of real-world vegetation.  You can set this to a value less than 1 to produce an artificially scarce distribution.  For example, 0.001 will produce 1/1000 of the normal density of vegetation.
3. The resulting VF file can be used by Enviro.

If you instead have polygon data which described the general area covered by a number of plants, use these steps to generate a vegetation distribution:

1. Load your Bioregion (list of Biotypes) with the menu command "Vegetation: BioRegions".
   An example file is in Data/PlantData/bioregion.txt
The plant densities are in plants per square meter.
2. Import at least one vegetation layer with Biotype.  Biotype is by 0-based index, so a integer field with values of 0, 1, 2, 3 etc. indicates which biotype.
3. If you also (optionally) have polygon data with additional information about plant density, import that layer as Density.  This can be the same GIS file that contains the Biotype, or a separate file such as a LULC file.  If you don't have a data file, the default of "Normal Density" will be assumed.
4. Use the Area Tool to indicate the area in which to distribute the vegetation
5. Give the menu command "Area Tool - Generate Vegetation"  A dialog will ask for :
   • Grid Spacing of Sampling, in meters.  The distribution will occur on a regular grid.  At each point, it will test to see what kind of plant belongs at that location, given all known inputs.  Then, if a plant is generated, a small random offset is applied to avoid the "regular" look of an gridded distribution.
   • Artificial Scarcity.  Most interactive simulation can't handle the full density of real-world vegetation.  You can set this to a value less than 1 to produce an artificially scarce distribution.  For example, 0.001 will produce 1/1000 of the normal density of vegetation.
6. A VF file will be produced.  You can load this file back into VTBuilder to check for correct distribution, or you can load it into Enviro for 3D visualization.

Please email any questions.